> I think this is just way too simplistic of a view of it. People won't just follow two exact patterns of behavior regardless of their environment. We all have, to varying extents, a proclivity to instant dopamine-based gratification.

Perhaps in the same way as an LED dimmed via pulse-width modulation has, to a varying extent, a proclivity to not produce light? Then just as the human perception of such an LED is on a continuum between "off" and "full brightness", so people's net-worths-at-retirement will stand on a continuum between starvation and Bill Gates.